1. Field of the Invention
This invention relates to exposure information display devices for use in cameras, and more particularly to such display device usable for displaying both the amount of charge in the flash unit and the object distance in a combined form.
2. Description of the Prior Art
In the art of leaf shutter cameras, cameras with an automatic focusing device, strobe device and automatic exposure device have been more and more popular, and this trend has recently become more general. Among cameras on market, there is known one type of camera which displays whether an object to be photographed lies in a near or a far distance by using a distance information measured by an automatic focusing device, and in a stroboscopic exposure mode, the indication that the object is beyond the coupling range of the strobe, or at a farther distance than that which gives a proper exposure for the object in the flash mode is changed from a continuous illumination to a blinking illumination, thus warning the photographer. In the camera of above type, however, because the exposure operation is hindered from starting until the main capacitor of the strobe is fully charged, the aforesaid coupling range is retained constant. This constitutes a drawback.
Another type of camera has been put on the market by Canon Kabushiki Kaisha which enables emission of stroboscopic light even before the main capacitor is fully charged, by providing the level for determining the completion of charging of the main capacitor at a relatively low value with a small capacitance of an electrical power source or battery to minimize the size of the strobe device. In the above camera, from the moment at which the voltage on the main capacitor has reached a level for emission of light to the moment at which the main capacitor will be fully charged, the amount of charge on the main capacitor gradually rises along the lapse of time, leading to gradual increase of the amount of flash light to be emitted when it is fired.
There is also known a camera in which the distance information preset manually in the distance adjusting ring of a photographic lens, the film speed information and the information of the amount of charge on the main capacitor of the strobe are combined to control operation of the diaphragm in the objective lens so as to derive a proper exposure. In this type of camera, despite the amount of charge on the main capacitor changes with time, it is made possible to always obtain a proper exposure. In the event the proper exposure cannot be derived even with the diaphragm of the objective lens at full open, the camera is automatically hindered from entering the exposure making state. Since the camera, however, has no auto-focus function, the display of the object distance and the display of indicating whether or not the object falls within the coupling range take completely different forms.